A friend of the man missing at Whangārei Falls says he was an international student from the Philippines.
He was studying in Auckland but travelled to Whangārei for a short summer break, and was at the falls in Tikipunga for an afternoon swim.
He went under the water while swimming and failed to surface.
The Police Dive Squad had been involved with the search but had not been able to find the man, the friend said.
"We are all very affected and are now speaking to victim support," said the friend, who said he saw the man go under the water.
Whangārei Falls is a popular summer swimming spot and tourist attraction.
A police spokeswoman said the search resumed today at 11am after it was called off last night.
"Search and Rescue are present as well," she said.
"Police are supporting the family."
One woman, who did not want to be named, said yesterday she was walking her dog at the falls and did not see what had happened, but heard a lot of screaming.
Police, Fire and Emergency and St John Ambulance were called to the scene at about 4.30pm yesterday.
The woman said someone had told her they were looking for someone in the water.
Groups of people had initially gathered at two viewing platforms at the top of the falls and were looking down at the base of the falls, before police ushered them back and cordoned off the area.
The woman said a group also gathered at the bottom of the falls.
Whangārei Falls will be closed until the search operation is complete.